Alcohol

Chocolate, Coffee and Caffeine

They can cause vomiting and diarrhea, panting, excessive thirst and urination, hyperactivity, abnormal heart rhythm, tremors, seizures and even death.

Citrus

It can cause irritation and possibly even central nervous system depression if ingested in significant amounts. Small doses, such as eating the fruit, are not likely to present problems beyond minor stomach upset.

Grapes and Raisins

Although the toxic substance within grapes and raisins is unknown, these fruits can cause kidney failure. Until more information is known about the toxic substance, it is best to avoid feeding grapes and raisins to dogs.

Milk and Dairy

Because pets do not possess significant amounts of lactase, milk and other dairy-based products cause them diarrhea or other digestive upset.

Those are just to name a few. Here is the link to see additional foods to avoid feeding your pets.